Method of manufacturing a mixture for tv glasses

ABSTRACT

The manufacture of a mixture for TV-glass whose composition lies within the following limits in % by weight:   with felspar having a specific surface &gt; 1 sq. m/g and quartz sand having a specific surface &lt; 0.1 sq. m/g.

United States Patent [1 1 Houben Dec.9,1975

[ METHOD OF MANUFACTURING A MIXTURE FOR TV GLASSES [75] Inventor:Mathijs Maria Hendrikus Houben,

Eindohoven, Netherlands [73] Assignee: U.S. Philips CorporatiomNew York,NY.

[22] Filed: Sept. 24, 1973 [21] App]. No.: 400,402

[30] Foreign Application Priority Data OTHER PUBLICATIONS CeramicIndustry 1967 Handbook of Materials for Ceramic Processing, p. 92.

Ceramic Age Micron-sized Silica available in Production Lots Sept. 1961,p. 34.

Primary ExaminerPatrick P. Garvin Assistant ExaminerJohn F Niebling.Attorney, Agent, or Fi rmFrank R. Trifari; Daniel R.

McGlynn [57] ABSTRACT The manufacture of a mixture for TV-glass whosecomposition lies within the following limits in by weight:

with felspar having a specific surface 1 sq. m/g and quartz sand havinga specific surface 0.1 sq. m/g.

1 Claim, No Drawings METHOD OF MANUFACTURING A MIXTURE FOR TV GLASSESThe principle of the measurement is as follows. An adsorption vesselcontaining the sample and a standard vessel of the same volume arefilled at room temperature with nitrogen having an atmospheric pressure.Subsequently the two vessels are introduced into liquid nitrogen. Theadsorption of nitrogen on the sample results in a pressure differencebetween the vessels. The quantity of adsorbed nitrogen can be calculatedfrom this pressure difference and the filling pressure of the nitrogenand subsequently the specific surface can be calculated. 7

Decisive factors in making the glass melt are particularly the freedomfrom bubbles of the'melt and, to a sio. 50-75 lesser extent, thedisappearance of crystalline constitu- A1 0 0.5-6 R20 13 (Lip K20 Na o)15 ents Pbo (H5 l The following scheme shows the effect of the inven-BaO 0 15 tion giving assessment marks ranging from 1 (satisfac- Zro2 (L8PbO BaO zro Sr0 8 tory) to 5 (poor) SrO 0 12 mixture assessment marksfelspar felspar quartz quartz disappearfree (a) (b) sand sand ance offrom spec. surf. spec. surf. 0.l 0.l crystalline bubbles l sq.m/g l sqm/g sqmlg sq.m/g constituents x x 1 4 x 1 5 X x 2 2 x 1 4 The mixturewhich is used for the manufacture of this The invention be described ireferellce type of glass comprises felspar xAlsi o and/or NaAlto someexamples In felspar havmg a speclfic Si O as a source for A1 0 quartzsand whose quan- Surface lm/g compared Wlth PQ tity is corrected for SiOfrom the felspar as a source for mg speclfic urface 1 m/g and Wlthquartz Sand SiO alkali carbonates and/or optionally alkali hydroxhavmg ap q Surface 9 qides for the suppletion of the alkali oxide and for theThe following mixtures g were remainder optionally minium, leadsilicate, barium car- P bonate, zirconium oxide or zirconium sand, inthe latter case, likewise as for lead silicate under correction of 1 2 34 the quartz sand to be added, and calcium carbonate, magnesite or d lit quartz sand 530 521 59l 509 felspar 174.4 164 102 135 sodiumcarbonate 141 131 124 134 Accordlng to the lnventlon 1t was found thatan imq 70 portant acceleration of the melting process can be z isgzz' g2 i2 achieved as udged with respect to the freedom from barium carbonate164 14.2 175 175 bubbles in the glass melt and the dissolution ofcrystal- Silicate 3 I line constituents if sodium powder and/or felsparpowdol mit v der 15 used in the glass mixture whose specific surface isantimmly Pg g 2 5 7 6 larger than 1 sq. m/g in addition to quartz sandwhose $111332: 0:5 2 speclfic surface 15 less than 0.1 sq. m/g. sodiumnitrate 15 10.2 5 15 According to the invention it was found that in themixture the felspar powder must satisfy the given re- A portion of 60 gof these mixtures was melted in air at quirement relating to a minimumspecific surface l430C in a platinum crucible in an electric furnacethereof. under quick heating (within approximately 5 min. to l430C). Thestep according to the invention was It was, however, also remarkablethat the optl mum found to reduce the time when the melt was free fromeffect of a shorter melting perlod was only achieved bubbles fromapproximately 120 min. to min. in all when the quartz sand also had amaximum specific surf r c face- 60 The glasses obtained have thefollowing composition in by weight: The speclfllc surface of fine andporous solld materials is determined in a simple manner by means of the1 2 3 4 area meter. The method on which the determination by s i0 64.272.8 67.l 61.4 means of thls apparatus 1s based, namely adsorptlon of b91 86 H 8.8 nltrogen at a low temperature was developed by K20 6.6 9.16.1 7.8 Brunauer, Emmet and Teller and later-simplified by R. 5:8 6 5'2Haul and G. Dumbgen (Chem. lng. Techn. 32, zroz 349-354 (1960) and 35,586-589 (1963). Mgo L2 -continued PbO 12.0 3.3 M203 3.3 3.1 1.9 2.6 Sb O0.6 0.5 0.4 0.6 020, 0.2 ()1 SrO 0.1 0.1 Fe O 0.1

What is claimed is:

1. A method of manufacturing a glass mixture intended for themanufacture of glasses for the screen of the cone of a cathode-ray tubefor television image display, comprising the steps of:

providing a mixture having the composition within the range limited asfollows in by weight:

consisting of a pulverulent mixture of feldspar, quartz sand and otherglass-forming components, wherein said feldspar has a specific surfacelarger than 1 sq. m/g and said quartz sand has a specific surfacesmaller than 0.1 sq. m/g and producing a glass melt from said mixturesubstantially free from bubbles and having enhanced dissolution ofcrystalline constituents.

1. A METHOD OF MANUFACTURING A GLASS MIXTURE INTENDED FOR THEMANUFACTURE OF GLASSES FOR THE SCREEN OF THE CONE OF A CATHODE-RAY TUBEFOR TELEVISION IMAGE DISPLAY, COMPRISING THE STEPS OF: PROVIDING AMIXTURE HAVING THE COMPOSITION WITHIN THE RANGE LIMITED AS FOLLOWS % BYWEIGHT: